This invention relates to the lining of pipelines and passageways especially but not exclusively underground pipelines or passageways by the so-called soft lining or cured in place method.
In this method, a tubular liner of resin absorbent material surrounded by a coating membrane or film of an impermeable material is soaked in a curable synthetic resin, and then the lining tube whilst still flexible i.e. the resin is uncured, is inflated by any suitable fluid medium such as air or water onto the underground pipeline or passageway surface. Whilst the lining tube is so held, the resin is cured or caused to cure so that it hardens into a substantially rigid pipe within the existing pipeline or passageway, the absorbent material being embedded in the cured resin. The process is used mainly for the relining of sewers; it provides first class rehabilitation of sewers and it has been tremendously successful.
An extremely effective pipelining construction results, and in fact the pipelining is carried this way throughout the world and to a considerable extent.
The examples of the method are disclosed in U.S. Pat. Nos. 4,009,063 and 4,064,211 which show that the lining tube may be inserted in the pipeline or passageway by any of several methods including an eversion method in which one end of the lining pipe is held at one end of the length of passageway to be lined, and the remainder of the lining tube is everted through the held end by a suitable fluid, usually water, in order simultaneously to apply the lining tube to the pipeline or passageway surface, and to hold it to such surface whilst curing takes place.
In an alternative method, referred to as pull in and inflate, the lining tube is simply inserted for example by pulling into the pipeline or passageway and then is inflated up to the pipeline or passageway surface by any suitable means such as an inflation tube which is everted into the inside of the lining tube.
A combination of these installation methods has been proposed and used in that two impregnated lining tubes may be used, a first of which is pulled into the pipeline or passageway and the second of which is everted into the first when it is inside the pipeline or passageway.
As to the method of curing the resin when the lining tube is in place, whilst other methods of curing resin have been proposed, such as curing by light radiation or by ultrasonics, by far the vast majority of cured in place lining work involves curing of the resin using heat. The most common resin which is used for impregnating the lining tube is polyester resin which is a heat cured thermosetting resin.
The present invention relates to improvements in soft lining processes wherein heat is used to cure the resin, and whilst the resin may typically be polyester resin, it is to be mentioned that any other heat cure resin may be employed.
In the known processes involving heat curing, it is ususal for the inflated lining tube to be filled with hot water in order to effect or at least initiate the cure. It should be mentioned that polyester resin is self curing once the initial curing reaction process has commenced, in that the reaction is exothermic which means that the curing of the resin in itself generates heat and that heat in turn enhances the curing rate.
As mentioned above, when curing by heat takes place, it is usual to fill the entire lining tube with hot water. As can be appreciated, especially in the case of pipelines or passageways of substantial diameter and/or length, large volumes of hot water must be provided, and this in itself represents a considerable problem. It is usual to provide the hot water from a supply vehicle such as a lorry or truck which is provided with a boiler and is connected to a supply of cold water. Heating of such a large volume of water takes a considerable length of time and costs a lot of money and this results in that completion of the lining operation is delayed due to the fact that a large volume of hot water must be brought up to temperature, and furthermore must be maintained at temperature in order to effect the cure, and the cost of the lining operation is increased. Because large volumes of water are involved, it is not possible to raise the temperature higher than a safe limit because of danger to personnel, and this again has a limiting effect on the speed of operation.
Where the lining tube is to be applied, as in the usual case to underground sewers, it is usual for the lining tubes to be applied during the night when the majority at least of the adjacent population will be asleep, so that there is minimum disruption. It is therefore of critical importance that the lining operation should be performed in as short a time as possible. When the lining tube has been applied it is therefore desirable that curing of the resin should be completed or at least initiated in as short a time as possible. The time can be reduced by using a fluid medium which is at a higher temperature, because generally the higher the fluid temperature, the greater the rate of curing, but there are temperature limitations for the reasons given above.
The present invention has an object to enhance the process whereby the curing time may be reduced, and curing can be effected in a particularly effective manner.
In accordance with the present invention there is provided a method of lining a pipeline or passageway wherein a lining tube comprising resin absorbent material which is impregnated with heat curable synthetic resin is urged by pressure against the pipeline or passageway surface, and heat is applied in stages to lengths of the lining tube by the following steps
a) a first length is isolated from the remainder of the lining tube by expanding expansible and contractible means located inside the pipe,
b) heated fluent medium is supplied to inside said first length so that the heat therein cures the resin in said first length,
c) the expansible and contractible means is contracted and moved to a new position along the inside of the lining tube,
d) the expandible and contractible means is expanded to isolate a second length of lining tube,
e) heated fluent medium is supplied to inside said second length so that the heat therein cures the resins in said second length and
f) if necessary, repeating the above steps for third and further lengths of the lining tube in order to complete the cure of the resin throughout the lining tube.
Preferably the resin is cured along the length of the tube in sections and in a sequence of operations comprising curing the resin of a first section or initiating the cure thereof, followed by curing of the resin of a next adjacent section, preferably of a similar length to the first section. By proceeding in this way an added advantage is obtained in that when polyester resin is cured it undergoes shrinkage and if a long length of tube is cured where the resin throughout the tube is cured at the same time, this shrinkage can cause a problem. If the resin is cured in short lengths however the uncured adjacent section can accommodate the shrinkage of the curing portions.
The means for performing the method may comprise sealing or blocking collars positioned in said lining tube at the ends of each section as it is cured, and the hot fluid heating medium, hot air, steam or water or a combination of these, can be circulated through the interior of the pipeline or passageway only in that section.
Where the lining tube is everted into the pipeline or passageway, only one of the blocking collars need be used during the curing of the first section, and in this connection a second blocking collar preferably is capable of collapse and expansion so that it can be expanded for the curing of the adjacent and subsequent sections.
Where the lining tube is everted into the pipeline or passageway, on the trailing end thereof there may be connected an eye or loop through which a hold-back rope passes, the hold-back rope serving on the one hand to control the rate of eversion of the length of tube as it is being put into the pipeline or passageway, and on the other hand serving as a means for supporting a pair of inflatable collars forming said blocking means, the collars being collapsed as the tube is everted into the pipeline or passageway, and these collars being attached to one length of the hold-back rope, the other length passing freely through the collars.
Connected to each collar there may be an inflation hose by which air under pressure can be supplied to the collars or withdrawn therefrom to expand and deflate the collars from ground level.
Additionally, circulation hoses may be connected to at least one of the collars and preferably that collar which is further from the trailing end of the lining when it has been fully everted.
By controlling the supply of air under pressure to the collars, and by feeding the hold-back rope around the eye or loop following complete eversion of the lining tube, so the collars can be positioned in sequence at different sections of the lining tube, and the collars can be selectively inflated and deflated to permit this movement to take place, to permit displacement of the fluid from the section between the collars, and to blank off the section between the collars so that heating fluid can be circulated only through this section by means of the circulation hoses.
It will be seen that the invention provides that heating of the lining tube for initiating or effecting cure of the resin can take place in controlled steps.
As a relatively small amount of heating fluid is used, it may be permissible to use heating fluid at a much higher temperature than heretofore and in any case it will be possible to heat that fluid up to that temperature quicker and by using smaller on site equipment, all of which is desirable. Indeed, the heating fluid may be super heated steam so that a very high temperature can be applied over the section of lining tube being cured. As soon as cure has been initiated and the lining tube is free standing over that section, the collars can be moved to the next section and the heating fluid circulated in the space therebetween to commence the cure of the next section.
It is believed that by performing the curing in this manner, the cure time can be considerably reduced especially if a medium at a much higher temperature can be used, and this will be of particular advantage in the curing of linings in large diameter and/or length pipes or passageways.
The spacing between the collars can be selected to suit the volume of hot fluid which can be supplied by the heating means, consistent with achieving a rapid rate of cure of the resin.